1. Field of the Invention
The present invention concerns the affixing of removable faceplates to the jaws of a machine vise by means of fasteners passing within keyhole apertures.
2. Background of the Invention
A vise is a common means of holding a workpiece during machine operations. The workpiece is placed between the open jaws of the vise and the jaws are then tightened, clamping the workpiece securely. The vise is sometimes positionally and/or rotatably adjustable in order to position the workpiece during machining operations. At the conclusion of machining operations the vise is opened and the processed workpiece extracted.
It is known to use removable faceplates on the jaws of machinist's vises in order to better support grasping and clamping the workpiece. The removable faceplates may be, for example, of a relatively softer metal material, for example aluminum, than the strong metal material, normally steel, from which the jaws are typically made. The removable faceplates may also present contours such as V-grooves, steps, and/or serrations which are particularly suitable to the grasping and holding of individual workpieces. Indeed, the contours of a removable faceplate may be made in a custom contour as besuits the effective contacting and holding of a particular workpiece or type of workpiece.
A vise jaw removable faceplate is positioned and secured to the operative side of a vise jaw that is adapted for fitting such a removable faceplate. The removable faceplate typically has equal width and depth to the normal jaw of the vise. The removable faceplate is typically of adequate thickness so as to permit it to be (i) securely affixated to the vise jaw and (ii) pressured into grasping contact with the workpiece without undue distortion. For example, for a typical vise jaw having a 6" width and a 13/4" depth, a removable jaw faceplate would typically be 6" wide by 13/4" depth by 13/16" thickness. Two such opposed removable faceplates reduce the maximum gap between the open vise jaws (for example, by twice 13/16", or 1 10/16") but this reduction is normally not a problem.
The present invention particularly concerns the manner by which removable faceplates may be fixed to the permanent jaws of a vise. One previous method of affixing removable faceplates to vise jaws is by machine bolts threading round holes within the removable faceplates. The diameter of the holes is typically countersunk to an adequate depth so as to permit the heads of the bolts to be recessed below the surface of the faceplate, making that the operative face of the faceplate presents a flat surface from which the bolt heads do not protrude.
One type of bolt that is typically used to affix removable faceplates is an allen-headed bolt having an internal hexagonal aperture that fits an allen wrench. The particular type of bolt is, however, important neither to the affixation of the previous removable faceplates nor to the removable faceplate of the present invention. It merely sufficient that the head of the bolt or other fastener should present a shoulder which fits against a corresponding lip of an aperture within the removable faceplate in order to secure the removable faceplate to the vise's jaw by tightening of the bolt.
A problem exists with the previous affixation of vise jaw removable faceplates to vise jaws by bolts passing through round apertures (which apertures may be countersunk). Mainly, each removal and substitution of the removable faceplate requires the complete extraction and reinsertion of the one or more securing bolts. Removable faceplates may be interchanged quite frequently during a machining operation. Faceplates are normally freely interchanged as best besuits the differing surfaces of the same or of different workpieces to be, at different times, held within the vise jaws. During each such interchange the securing bolts, typically two in number, to the removable faceplate must be completely unscrewed. A substitutionary removable faceplate is then positioned in place. The same bolts are rethreaded into the same holes and retightened.
Because the transverse forces that are transmitted to the removable faceplate during machining of a held workpiece may be very high, the bolts are typically substantial. The bolts are typically of 1/2"-13 diameter for the previously-mentioned typical 6" width vise jaw. This 1/2" bolt is also threaded into the permanent jaws for a considerable depth in order to provide adequate strength, typically for a depth of 1/2 or greater. This means that each interchange of a previous vise jaw removable faceplate, of which there are typically two upon each vise, requires that two bolts should be (i) unthreaded over a distance of 1/2, (ii) extracted from the round apertures of the vise jaw removable faceplate and temporarily stored, (iii) passed through the round apertures of the substitutionary vise jaw removable faceplate, (iv) rescrewed into the threaded holes of the vise jaw, and (vi) tightened. Although routinely performed, this procedure is time consuming and not as efficient as would be desired.
Meanwhile, it is generally known in the mechanical arts that bolted affixation of members may transpire by use of a keyhole aperture within one of the affixed members. A keyhole aperture is an elongate hole, or slot, which has a relatively greater diameter at one end of the hole, or slot, than at the other end. The smaller and larger diameters of the aperture are respectively complementary in size to the shank and head of a bolt which is received within such aperture. The head of the bolt, which is typically round, will pass through the larger diameter portion of the keyhole aperture but will not pass through the smaller diameter portion. The shank of the bolt will pass through both portions of the aperture.
The action of affixing members by passing bolts through keyhole apertures does not require that a bolt should be completely extracted from one member in order to fit and to attach another member that presents a keyhole aperture. Rather, the wider portion of the keyhole aperture within the one member passes the head of the bolt. This one member is then moved transversely so that the bolt head is within the narrow diameter region of the keyhole aperture. At this location the bolt is further tightened so as to contact the shoulders of the keyhole aperture at the region of its narrow diameter. By this tightening the two members are securely attached.
A keyhole aperture may be countersunk in order to permit the heads of the bolts which thread it to fit flush with, or below, the surface of the member presenting the keyhole aperture.